1. Field of the Invention
The present invention relates to a heat treatment device and, more particularly, to a local resistance heating device with a controlled atmosphere able to provide only a part of a workpiece with an inert gas to process a resistance heating treatment.
2. Description of the Related Art
Conventionally, in accordance with the heat source, heat treatments can be roughly divided into two kinds: a burning heating method and an electric heating method. The electric heating method further includes a resistance heating treatment, a conduction heating treatment, an electrical heating treatment, and a laser heating treatment.
Moreover, the resistance heating treatment can further be categorized into a direct heating way and an indirect heating way. The direct heating way conducts electricity directly to a workpiece to heat the workpiece via the heat induced by the resistance of the workpiece itself. The indirect heating way puts a workpiece into a heating furnace and controls the temperature of a gas received in the heating furnace by the heated pieces arranged inside the heating furnace, to heat the workpiece by the heated gas. Specifically, inert gas such as argon and helium can be taken as the gas received in the heating furnace for avoiding oxidation of the workpiece during processes of the heat treatment.
However, in the condition that only a part of the workpiece has to be heated or the volume of the workpiece is small, an inner space of the heating furnace still has to be filled with the inert gas to activate the anti-oxidation function, and this will lead to a large consumption of the inert gas and thus a great cost. Besides, the size of the workpiece is limited by the inner space of the heating furnace for the heating furnace to completely receive the workpiece and to proceed with the heat treatment. Furthermore, an even thermal environment provided by the heating furnace is hard to achieve, since the heat is generated by the plural heated pieces, and thus results of the heat treatment are usually not good enough. In light of this, it is desired to improve the conventional resistance heating device.